TDS and conductivity converter
Convert between electrical conductivity and TDS with an adjustable conversion factor, and see the typical water classification for the result.
Results
| TDS | 960 mg/L |
|---|---|
| Conductivity | 1 500 µS/cm |
| Conductivity in mS/m | 150 |
Roughly 960 mg/L TDS: within the SANS 241 aesthetic limit, palatability declining. This is a concentration, not a verdict on safety: TDS carries no information about bacteria, nitrate, fluoride or metals, so it cannot establish that water is fit to drink. The EC–TDS factor depends on the ion mix, and the two common instrument scales run the opposite way to most people’s guess: ~0.5 for NaCl-dominated water, ~0.65–0.7 for the mixed-salt (“442”) scale meant for natural waters. Handheld TDS meters measure conductivity and apply a fixed factor, so check which scale yours uses before comparing readings.
Formula used
TDS = EC × f
EC (mS/m) = EC (µS/cm) ÷ 10
- TDS
- total dissolved solids, mg/L
- EC
- electrical conductivity at 25 °C, µS/cm
- f
- conversion factor: ~0.5 NaCl scale, ~0.65–0.7 mixed-salt (442) scale for natural waters (default 0.64)
The factor depends on the ion mix and on the instrument scale: ~0.5 for the NaCl scale, ~0.65–0.7 for the mixed-salt (442) scale intended for natural waters, with 0.64 a reasonable general-purpose value for South African borehole water. Handheld TDS meters measure EC and apply a fixed factor; check which scale yours uses before comparing readings. Conductivity is temperature-sensitive; meters normally report the 25 °C-compensated value. TDS is an aesthetic and process number: it cannot establish potability.
The background
- TDS, EC and what conductivity actually tells youTotal dissolved solids and electrical conductivity are the first numbers on any water analysis. Here is what they measure, how they relate, and what they cannot tell you.
- Permeate quality: what TDS to expect and why it driftsRO permeate is very good water, though never perfect, and its quality moves with temperature, recovery, pressure and time. What to expect, what is normal drift, and what is a fault.
- Laboratory water grades: Type I to Type III, ISO 3696 and CLRWLab water is graded, and the grades are not interchangeable. What the ASTM, ISO and CLSI specifications say, the RO-plus-polishing systems that produce them, and what to feed an autoclave.
Equipment for this duty
Send the water analysis and duty point, and the branch confirms exact selections, pricing and lead times, usually within one working day.
Request a quoteResults are indicative engineering estimates based on standard formulas and typical assumptions. They are not a design service; confirm any design against a full water analysis and the relevant manufacturer’s data.